Method of protecting a component of a turbomachine from liquid droplets erosion, component and turbomachine

Abstract

The method of protecting a component of a turbomachine from liquid droplets erosion provides covering at least one region of a component surface exposed to a flow of a fluid containing a liquid phase to be processed by the turbomachine with a protective layer. The protective layer consists of a plurality of adjacent sub-layers of different materials having high hardness in the range of 1000-3000 HV and low fracture toughness below 20 MPam1/2. The materials are typically nitrides or carbides of titanium or aluminum or chromium or tungsten. In an embodiment, the covering is carried out by a PVD technique, in particular by Cathodic Arc PVD, or a CVD technique. The method may be applied to any component of turbomachines, but it may be particularly beneficial for parts of centrifugal compressors.

What is claimed is: 
     
       1. A method of protecting a component of a turbomachine from liquid droplets erosion, the method comprising:
 covering at least one region of a component surface exposed to a flow of a fluid containing a liquid phase to be processed by the turbomachine with a protective layer, 
 wherein the protective layer comprises a plurality of adjacent sub-layers of two materials in alternate position, 
 wherein the materials have high hardness in the range of 1000-3000 HV and low fracture toughness below 20 MPam 1/2 , and 
 wherein a first material of the two materials is a stoichiometric nitride or carbide or boride of titanium or zirconium or chromium or tungsten or aluminum or vanadium, and a second material of the two materials is a non-stoichiometric nitride or carbide or boride of titanium or zirconium or chromium or tungsten or aluminum or vanadium. 
 
     
     
       2. The method of  claim 1 , wherein the materials are Titanium Nitride (TiN). 
     
     
       3. The method of  claim 1 , wherein the covering is carried out by a CVD technique. 
     
     
       4. The method of  claim 1 , wherein the covering is carried out by a PVD technique. 
     
     
       5. The method of  claim 4 , wherein “targets” for the Cathodic Arc PVD are located and/or shaped so that at least the targets see directly or indirectly parts of the at least one region of the component surface to be covered. 
     
     
       6. A component of a centrifugal compressor having a surface exposed to a flow of a fluid containing a liquid phase to be compressed by the centrifugal compressor, the component comprising:
 at least one region of the surface covered with a protective layer, 
 wherein the protective layer comprises a plurality of adjacent sub-layers of two materials in alternate position, 
 wherein the materials have high hardness in the range of 1000-3000 HV and low fracture toughness below 20 MPam 1/2 , and 
 wherein a first material of the two materials is a stoichiometric nitride or carbide or boride of titanium or zirconium or chromium or tungsten or aluminum or vanadium, and a second material of the two materials is a non-stoichiometric nitride or carbide or boride of titanium or zirconium or chromium or tungsten or aluminum or vanadium. 
 
     
     
       7. The component of  claim 6 , wherein the component is a diaphragm, and wherein the surface exposed to fluid flow is covered by the protective layer entirely. 
     
     
       8. The component of  claim 6 , wherein the component is\an open impeller, and wherein the surface exposed to fluid flow is covered by the protective layer entirely. 
     
     
       9. The component of  claim 6 , wherein the component is a closed impeller, and wherein the surface exposed to fluid flow is covered by the protective layer only at the inlet zone of the channels and/or at the outlet zone of the channels. 
     
     
       10. The component of  claim 6 , wherein the component is an inlet guide vane, and wherein the surface exposed to fluid flow is covered by the protective layer entirely. 
     
     
       11. A centrifugal compressor, the centrifugal compressor comprising:
 a component having a surface exposed to a flow of a fluid containing a liquid phase to be compressed by the centrifugal compressor, the component comprising:
 at least one region of the surface covered with a protective layer, 
 wherein the protective layer comprises a plurality of adjacent sub-layers of two materials in alternate position, 
 wherein the materials have high hardness in the range of 1000-3000 HV and low fracture toughness below 20 MPam 1/2 , and 
 wherein a first material of the two materials is a stoichiometric nitride or carbide or boride of titanium or zirconium or chromium or tungsten or aluminum or vanadium, and a second material of the two materials is a non-stoichiometric nitride or carbide or boride of titanium or zirconium or chromium or tungsten or aluminum or vanadium. 
 
 
     
     
       12. The centrifugal compressor of  claim 11 , wherein the centrifugal compressor comprising a combination of components. 
     
     
       13. The centrifugal compressor of  claim 11 ,
 wherein the bulk material of the or each component is martensitic stainless steel or nickel-base alloy or cobalt-base alloy. 
 
     
     
       14. An axial compressor, wherein at least the blades of the first stage or stages have a protective layer for their protection according to  claim 1 . 
     
     
       15. A steam turbine, wherein at least the blades of the last stage or stages have a protective layer for their protection according to  claim 1 . 
     
     
       16. The centrifugal compressor of  claim 12 ,
 wherein the bulk material of the or each component is martensitic stainless steel or nickel-base alloy or cobalt-base alloy. 
 
     
     
       17. The method of  claim 1 , wherein the covering is carried out by a Cathodic Arc PVD. 
     
     
       18. The centrifugal compressor of  claim 11 , wherein the component is a diaphragm, and wherein the surface exposed to fluid flow is covered by the protective layer entirely. 
     
     
       19. The centrifugal compressor of  claim 11 , wherein the component is an open impeller, and wherein the surface exposed to fluid flow is covered by the protective layer entirely. 
     
     
       20. The centrifugal compressor of  claim 11 , wherein the component is a closed impeller, and wherein the surface exposed to fluid flow is covered by the protective layer only at the inlet zone of the channels and/or at the outlet zone of the channels. 
     
     
       21. The centrifugal compressor of  claim 11 , wherein the component is an inlet guide vane, and wherein the surface exposed to fluid flow is covered by the protective layer entirely.